Stochastic Resonance (SR) is a well-known phenomenon that occurs in different macro, micro and even nano systems. SR allows for improving the detectability of a signal below a threshold by injecting a noise into the systems. Therefore, SR appears to be an interesting and attractive phenomenon to be applied in sensory systems in order to improve the sensitivity of the subject's sensory, reflex and/or motor mechanisms.
Indeed, it has been shown that, when a weak sensory stimulus applied to an individual, for stimulating a specific sense, is added with an appropriate amount of white noise, the weak sensory stimulus can then be detected and thus activate the reactions of that particular sense in response to the applied weak sensory stimulus.
For example, in “The Benefits of Background Noise”, a paper written by Frank Moss and Kurt Wiesenfeld, for Scientific American Inc., in 1995, the role of SR was investigated in biological sensory systems. For that purpose, the fine hairs in a crayfish's tail were under test. The fine hairs can detect motions, such as water motions caused by the arrival (movement) of a potential predator. In the experimental set-up, a crayfish's tail was isolated and mounted to a post and then placed inside a tank containing a saline solution. Also, an electrode was inserted in the nerve cord connected to the hairs, in order to measure the level of nerve impulses generated by the nerve, in response to the motions of the post detected by the hairs. A random noise was then added to the signal moving the post so as to create fluctuations in the motions of the post. Results showed that the sensitivity of the fine hairs was increased and the results exhibited the SR phenomenon.
It is further suggested in the same paper that SR has practical applications in the field of medical science and more specifically in the nervous system of human beings. In the same way, the paper entitled “Stochastic Resonance in Psychophysics and in Animal Behavior”, by L. M. Ward et al., published in Biological Cybernetics, 87, 91-1001, in 2002, states that SR can be used for improving human performance through auditory, visual and tactile sensory systems since they contain a neural system.
Regarding Japanese patent application JP2003048453 A2, entitled “Display Device for Vehicle”, by Hirose Satoro, published in 2003, a device is provided for a driver's car for increasing the driver's awareness of the surroundings and for keeping his/her attention focused on the road. To do so, a plurality of embodiments of the device has been developed, using different sensory stimulations, such as a visual, auditory or vibratory stimulation. The different embodiments were installed on the side mirrors of the car, on the steering wheel, etc. Each embodiment comprises a noise generator for producing a noise necessary for improving the perception of the driver according to the SR phenomenon. However, this device is meant for use only with car driving.
In US Patent Application No. 2004/0073271 A1, entitled “Method and System for Neurophysiologic Performance”, by J. D. Harry et al., published in 2004, a system for improving neurophysiologic performance is disclosed. The system consists of a garment which comprises at least one input signal device that can be positioned at different locations on the garment, and one signal generator. The input signal device, such as electrodes or muscle stimulators, allows for inputting a bias signal to sensory cells for improving the functions thereof during a physical activity. The bias signal is generated by the signal generator. This system mainly focuses on contact stimulations through the skin.
In US Patent Application No. 2004/0173220 A1, entitled “Method and System for Improving Human Balance and Gait and Preventing Foot Injury”, by J. D. Harry et al., published in 2004, a wearable device such as a shoe insert or a sock for shoes is disclosed. The wearable device comprises electrodes and vibratory actuators for producing vibrations so as to stimulate the feet and ankles of an individual. Furthermore, the wearable device also comprises a signal generator for generating a random noise to be added to the vibrations. Using the SR principle, the wearable device allows for improving the gait and balance of the individual. This device is used only for foot stimulations.
So far, it has been shown that the principle of SR can be applied in a uni-modal way, meaning that both the signal and the noise are applied to a same receptor. For example, to enhance the tactile sensitivity, a tactile stimulus and a tactile noise are applied to a tactile mechanism, and to enhance the visual sensitivity, a visual stimulus and associate noise are applied to a visual mechanism.
However, so far, it has never been shown how to stimulate one subject's sensory mechanism with noise to affect another sensory, reflex and/or motor mechanism of the same subject, and how the noise acts upon a multi-sensory integration system.